There are a few smiths out there who don't mind having visitors while they work. If I remember right one of Ono Yoshimitsu's deshi would occasionally hold a class where the participants would forge out and heat treat their own kogatana (the small blade sometimes seen in the saya on the side of the sword). Very cool stuff for participants.

I've had the honor of hanging out watching a forging session (but no where near as involved as Peter was). Man, it is intense. I was standing close by and it wasn't until it was over that I realized I had multiple burn holes in my shirt and a few burns on my face. The smith later slapped me on the back saying I was a smith at heart the way I was standing in close without concern of the heat and sparks. He said I had that look in my eyes. Yeah, firebug I guess. It was truly fascinating. And I'm pretty sure I don't want to be the one swinging those hammers. One of these days I'm going to finish building my own forge here at home...